rappel vs rope down

rappel is a noun but rope down is not a noun.

Word	Noun	Adjective	Verb	Adverb
rappel	Yes	No	Yes	No
rope down	No	No	Yes	No

As verbs, rappel and rope down are synonyms defined as:

Other synonyms of rappel include abseil.

rappel (noun)	rope down (noun)
(mountaineering) a descent of a vertical cliff or wall made by using a doubled rope that is fixed to a higher point and wrapped around the body

rappel (verb)	rope down (verb)
descend by means of a rappel	descend by means of a rappel